Intermediate 2 Chemistry. PPA Revision

Joat Services Intermediate 2 Chemistry Starter Pack 2001 – 2002

Intermediate 2 Chemistry. PPA Revision

Unit 1 / Unit 2 / Unit 3
Effect of Concentration on the Rate of Reactions / Testing for Unsaturation / Preparation of a Salt
Effect of Temperature on the Rate of Reactions / Cracking / Factors which Affect Voltage
Electrolysis / Hydrolysis of Starch / Reaction of Metals with Oxygen

Unit 1

Effect of concentration on rate.

Often called the iodine clock reaction.

Persulphate and potassium iodide

Rate is the inverse of time. Unit s-1

All other factors must be kept the same.

The change is sudden due to presence of Iodine the starch changes colour turns black.

Easily measured change

Safety, eye protection and care not to come in contact with the skin

Effect of heat on rate

Thiosulphate on a cross, add Hydrochloric acid.

Forms fine powdered (colloidal) sulphur. Which obscures the cross

Errors include when exactly does the cross disappear.

Keeping temperature constant is difficult

Electrolysis of copper(II) chloride

Watch the animation

Danger of Chlorine, a toxic gas

Electrolysis cell 2 carbon electrodes

One turns brown –ve

One a gas is evolved +ve

Moist universal indicator paper turns red.

Smell Very carefully

Unit 2

Testing for unsaturation.

Small amount of hydrocarbon

Add bromine water

Shake by waggling, do not allow any chemicals in contact with the skin.

Alkenes turn the bromine water from brown to colourless(not clear)

Cracking

Mineral wool and paraffin

Catalyst aluminium oxide

Heat in a tube.

Gas given off, therefore smaller molecules

Decolourises bromine water therefore unsaturated

Do not stop heating until you have removed the tube from the water, suck back shatters the tube.

Hydrolysis of Starch

Enzyme is amylase

Experiment conducted at 37oC

Benedicts solution shows that a simple reducing sugar is produced after 5 mins, colour change blue to orange

Repeat at high temperature using Hydrochloric acid

Acid must be neutralised before testing with sodium hydrogencarbonate

Unit 3

Preparation of a salt.

Insoluble magnesium carbonate is used so that it can be filtered off after reaction stops

No more gas given off shows reaction has stopped

Volume of water reduced by heating, boiling causes splashing

Note the shape of all the crystals is the same

Factors affecting Voltage

Keep all parameters the same except the one you are measuring and the one you are changing.

Metals, concentration of solution, solution used, volume of solution, how far apart the electrodes, are how deep in the solution the electrodes are, are all possible measurable variable

Repetition is a way of verifying that the results are correct.

Reaction of metals with oxygen

Potassium permanganate is a source of oxygen.

Heating the metal in a stream of oxygen causes it to react,

The higher the metal is in the ‘Electrochemical Series’ Page 7 data book the more reactive it is.

Magnesium burns very brightly.

Danger test tube must never point at anyone but across the bench.

General Safety Considerations

Always wear safety specs.

Be aware of danger labels

Never touch chemical with bear hands

Always read safety labels

Know what the dangers are before conducting an experiment

Heat makes ant chemical unsafe

Never sit when conducting experiments